Tensioning devices, also commonly known as belt tightener devices, are used to transport goods, to secure the load to the respective means of transport; for example, to fix the goods on the body of a truck or secure boats on the trailer during transportation or even to fix loads on car roof racks.
The most widespread known type of devices comprise a reel for winding the belt, a support, a lever and a ratchet gear designed to allow reel rotation in one direction only.
The lever, the support and the reel are all connected by a pin which also forms a reel axis of rotation.
Operation of said type of device is rather simple and allows, with an alternating movement of the lever, the reel to be rotated, causing the belt to be wound on it; the alternating movement of the lever being allowed by the ratchet gear which ensures that the lever pulls the reel, making it rotate only in the direction of rotation in which the belt is wound, whilst in the opposite direction the lever moves freely so that it can return to its starting position for a new winding step.
The ratchet gear usually comprises two gearwheels positioned at the longitudinal ends of the above-mentioned pin, and two elements which engage with the gearwheels, or teeth, one of which performs the function described above of allowing rotation of the gearwheel and the reel in one direction only, whilst the other has the function of both stopping rotation of the reel, subject to the load consisting of the tension applied to the belt during the lever recovery stroke, and of maintaining the final belt tension.
The engagement elements are held in their operating positions by respective elastic springs and can be disengaged from the gearwheels by overcoming the opposing action of the elastic springs, to allow rotation of the reel in the opposite direction and belt unwinding from the reel.
Known tensioning devices of the type described above are not without disadvantages.
A first disadvantage is the fact that the engagement elements, sliding over other parts of the device, both during the winding movement and during the gearwheel disengagement step, generate significant friction with said parts and, moreover, since all of the components of the device are substantially external, it is impossible to effectively lubricate them.
Another disadvantage is the large longitudinal dimensions of the known devices, not just during winding operating steps but also in the non-operating condition.
Since, for example, the reel is usually released after reaching the maximum relative opening condition between the support and lever, it is often the case that due to the large dimensions of the device, after tensioning the belt, it is realised that there is insufficient space to easily release the reel and for subsequent belt unwinding.
Another disadvantage linked to the use of the known devices is the fact that it is impossible to rapidly release the belt.
This failure is noticed above all in cases in which rapid release could affect user safety.